Method for preparing pre-coated aluminum alloy articles and articles prepared thereby

Abstract

An aluminum-alloy article such as a fastener is prepared by providing an aluminum-alloy article precursor that is not in its final heat-treated state, and in one form is in its solution treated/annealed state. A curable organic coating material is also provided. The method includes anodizing the article precursor, preferably in chromic acid solution and without chemical sealing during anodizing, applying the organic coating material to the aluminum-alloy article precursor, and precipitation heat-treating the coated aluminum article precursor to its final heat-treated state, thereby simultaneously curing the organic coating. If the aluminum alloy temper is of the naturally aging type, it is optionally lightly deformed prior to precipitation treatment aging. The approach may also be applied to articles that are not solution treated/annealed and aged, by first overly deforming the article precursor so that the curing treatment of the coating also partially anneals the article precursor to the final desired deformation state.

What is claimed is: 
     
       1. An aluminum-alloy aircraft article prepared by the method comprising the steps of: providing an aluminum-alloy aircraft article precursor that is not in its final heat-treated state;   anodizing the article precursor;   providing a curable phenolic resin-containing organic coating material, the coating material having a non-volatile portion that is predominantly organic and is curable at about a heat-treatment temperature of the aluminum-alloy aircraft article precursor;   applying the phenolic resin-containing organic coating material to the aluminum-alloy aircraft article precursor;   heat-treating the phenolic resin-containing coated aluminum-alloy aircraft article precursor to its final heat-treated state at the heat-treatment temperature and for a time sufficient to heat-treat the aluminum and cure the organic coating; and   obtaining a coated aluminum-alloy aircraft article having a shear strength approximately equal to or greater than 24,000 psi.   
     
     
       2. The aluminum-alloy aircraft article prepared according to the method of claim 1 including an additional step, after the step of heat-treating, of fastening a first piece to a second piece using the heat-treated aluminum-alloy aircraft article.   
     
     
       3. An aluminum-alloy aircraft article prepared according to the method comprising the steps of: providing an aluminum-alloy aircraft article precursor that is not in its final heat-treated state;   anodizing the article precursor;   providing a curable phenolic resin-containing organic coating material, the coating material having a non-volatile portion that is predominantly organic and is curable at about a heat-treatment temperature of the aluminum-alloy aircraft article precursor;   applying the phenolic resin-containing organic coating material to the aluminum-alloy aircraft article precursor;   heat-treating the phenolic resin-containing coated aluminum-alloy aircraft article precursor to its final heat-treated state at the heat-treatment temperature and for a time sufficient to heat-treat the aluminum and cure the organic coating; and   obtaining a coated aluminum-alloy aircraft article having a shear strength approximately equal to or greater than the shear strength of an aircraft aluminum-alloy selected from the group consisting of series 2000, 4000, 5000, 6000 and 7000 series aircraft aluminum-alloys.   
     
     
       4. The aluminum-alloy aircraft article prepared according to the method of claim 3, including, after the step of heat-treating, the step of fastening a first piece to a second piece using the heat-treated article.